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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 835-846 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A two-phase model is presented for simulating the post-filling stage of injection molding of amorphous and semicrystalline materials. A finite-element scheme with quadratic shape function for the pressure is proposed. The melt is considered in terms of Hele-Shaw flow for a non-Newtonian fluid using a modified-Cross model with either an Arrhenius-type or WLF-type functional form to describe the viscosity under nonisothermal conditions; the compressible behavior of the polymer is assumed to obey either a double-domain Tait or single-domain Spencer Gilmore equation of state. The interfacial energy balance equation including the latent-heat effect for semicrystalline materials is coupled with the transient energy equation for the solid and melt phases in order to predict the solidified layer and temperature profile. Two well-characterized materials, namely a commercial-grade PP and PS, were used in the present work. Good agreement is obtained between the present simulation and experimental pressure traces from this study and from previous investigation in the literature. The effects of compressibility, viscosity model, and thermal properties upon the predicted pressure field are also considered.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1039-1050 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A two-phase model is presented for simulating the injection mold filling process including the effect of transient melt solidification, i.e., the phase change effect. The liquid region is governed by Hele-Shaw flow for a non-Newtonian fluid using a modified Cross model to describe viscosity under non-isothermal conditions. Further, the energy equation of the solid phase is dominated by a transient condition. The interfacial energy balance equation is also proposed to predict the solidified layer thickness and temperature profile. Two well-characterized semicrystalline materials, polypropylene and polyethylene, were used in the present work. Good agreement is obtained between the predicted results and experimental observations from this study and the previous literature concerning the thickness of solid layer, the shape of, advancing melt front, and the pressure traces. In particular, the predicted pressure based upon the two-phase model is higher than that in terms of the single-phase model by about 13 percent. Finally, the semicrystalline structure of the frozen skin layer and the central core were investigated with a scanning electron microscope to verify the two-phase model.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A simple empirical relationship exists between the thickness and the solvent-evaporation rate of spin-coated thin films. The thickness of a film formed from an organic solvent solution can be approximated by the relationship\documentclass{article}\pagestyle{empty}\begin{document}$ D = K_0 \mu ^{0.36} \omega ^{ - 0.50} (E\lambda /C_p)^{0.60} $\end{document}, where μ is the viscosity of the coating solution, ω is the rotation speed, E is the solvent-evaporation rate, λ is the latent heat of evaporation, Cp is the heat capacity of the solvent, and K0 is a constant for volatile organic solvents. A similar relationship for aqueous polymer solutions is\documentclass{article}\pagestyle{empty}\begin{document}$ D = K_0 \mu ^{0.36} \omega ^{ - 0.50} (1.0 - RH)^{0.60} $\end{document}, where RH is the relative humidity of air around the spin coater and Ka is a constant for aqueous solutions. These relationships are helpful in understanding the mechanism of thin-film formation in spin coating.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 9 (1998), S. 549-552 
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C(4), C′(2)-Double substitution was achieved in good yields by reacting 3-arylsydnones with BuLi and then with a suitable electrophile in THF at -50°C. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:549-552, 1998
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2017-07-28
    Description: The water-gas shift (WGS) reaction (where carbon monoxide plus water yields dihydrogen and carbon dioxide) is an essential process for hydrogen generation and carbon monoxide removal in various energy-related chemical operations. This equilibrium-limited reaction is favored at a low working temperature. Potential application in fuel cells also requires a WGS catalyst to be highly active, stable, and energy-efficient and to match the working temperature of on-site hydrogen generation and consumption units. We synthesized layered gold (Au) clusters on a molybdenum carbide (α-MoC) substrate to create an interfacial catalyst system for the ultralow-temperature WGS reaction. Water was activated over α-MoC at 303 kelvin, whereas carbon monoxide adsorbed on adjacent Au sites was apt to react with surface hydroxyl groups formed from water splitting, leading to a high WGS activity at low temperatures.
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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